Implement asynchronous transfer queues, thread guards on RenderingDevice. Add ubershaders and rework pipeline caches for Forward+ and Mobile.

- Implements asynchronous transfer queues from PR #87590.
- Adds ubershaders that can run with specialization constants specified as push constants.
- Pipelines with specialization constants can compile in the background.
- Added monitoring for pipeline compilations.
- Materials and shaders can now be created asynchronously on background threads.
- Meshes that are loaded on background threads can also compile pipelines as part of the loading process.

servers/rendering/renderer_compositor.h

@@ -104,6 +104,7 @@ public:
 	virtual uint64_t get_frame_number() const = 0;
 	virtual double get_frame_delta_time() const = 0;
 	virtual double get_total_time() const = 0;
+	virtual bool can_create_resources_async() const = 0;
 
 	static bool is_low_end() { return low_end; };
 	virtual bool is_xr_enabled() const;